One known type of information storage device is a disk drive device that uses magnetic media to store data and a movable read/write head that is positioned over the media to selectively read from or write to the disk.
Consumers are constantly desiring greater storage capacity for such disk drive devices, as well as faster and more accurate reading and writing operations. Thus, disk drive manufacturers have continued to develop higher capacity disk drives by, for example, increasing the density of the information tracks on the disks by using a narrower track width and/or a narrower track pitch. However, each increase in track density requires that the disk drive device have a corresponding increase in the positional control of the read/write head in order to enable quick and accurate reading and writing operations using the higher density disks. As track density increases, it becomes more and more difficult using known technology to quickly and accurately position the read/write head over the desired information tracks on the storage media. Thus, disk drive manufacturers are constantly seeking ways to improve the positional control of the read/write head in order to take advantage of the continual increases in track density.
One approach that has been effectively used by disk drive manufacturers to improve the positional control of read/write heads for higher density disks is to employ a secondary actuator, known as a micro-actuator, that works in conjunction with a primary actuator to enable quick and accurate positional control for the read/write head. Disk drives that incorporate micro-actuators are known as dual-stage actuator systems.
Various dual-stage actuator systems have been developed in the past for the purpose of increasing the access speed and fine tuning the position of the read/write head over the desired tracks on high density storage media. Such dual-stage actuator systems typically include a primary voice-coil motor (VCM) actuator and a secondary micro-actuator, such as a PZT element micro-actuator. The VCM actuator is controlled by a servo control system that rotates the actuator arm that supports the read/write head to position the read/write head over the desired information track on the storage media. The PZT element micro-actuator is used in conjunction with the VCM actuator for the purpose of increasing the positioning access speed and fine tuning the exact position of the read/write head over the desired track. Thus, the VCM actuator makes larger adjustments to the position of the read/write head, while the PZT element micro-actuator makes smaller adjustments that fine tune the position of the read/write head relative to the storage media. In conjunction, the VCM actuator and the PZT element micro-actuator enable information to be efficiently and accurately written to and read from high density storage media.
One known type of micro-actuator incorporates PZT elements for causing fine positional adjustments of the read/write head. Such PZT micro-actuators include associated electronics that are operable to excite the PZT elements on the micro-actuator to selectively cause expansion and/or contraction thereof. The PZT micro-actuator is configured such that expansion and/or contraction of the PZT elements causes movement of the micro-actuator which, in turn, causes movement of the read/write head. This movement is used to make faster and finer adjustments to the position of the read/write head, as compared to a disk drive unit that uses only a VCM actuator. Exemplary PZT micro-actuators are disclosed in, for example, JP 2002-133803; U.S. Pat. Nos. 6,671,131 and 6,700,749; and U.S. Publication No. 2003/0168935, the contents of each of which are incorporated herein by reference.
FIG. 1 illustrates a conventional disk drive unit and shows a magnetic disk 101 mounted on a spindle motor 102 for spinning the disk 101. A voice coil motor arm 104 carries a head gimbal assembly (HGA) that includes a micro-actuator with a slider 103 incorporating a read/write head. A voice-coil motor (VCM) is provided for controlling the motion of the motor arm 104 and, in turn, controlling the slider 103 to move from track to track across the surface of the disk 101, thereby enabling the read/write head to read data from or write data to the disk 101.
Because of the inherent tolerances (e.g., dynamic play) of the VCM and the head suspension assembly, the slider cannot achieve quick and fine position control, which adversely impacts the ability of the read/write head to accurately read data from and write data to the disk when only a servo motor system is used. As a result, a PZT micro-actuator, as described above, is provided in order to improve the positional control of the slider 103 and the read/write head. More particularly, the PZT micro-actuator corrects the displacement of the slider on a much smaller scale, as compared to the VCM, in order to compensate for the resonance tolerance of the VCM and/or head suspension assembly. The micro-actuator enables, for example, the use of a smaller recording track pitch, and can increase the “tracks-per-inch” (TPI) value for the disk drive unit, as well as provide an advantageous reduction in the head seeking and settling time. Thus, the PZT micro-actuator enables the disk drive device to have a significant increase in the surface recording density of the information storage disks used therein.
FIG. 2a is a partial perspective view of an HGA 277 having a conventionally designed micro-actuator, FIG. 2b is a partial perspective view of the tongue region of the HGA of FIG. 2a, and FIG. 2c illustrates how a slider and micro-actuator conventionally are mounted to each other. With respect to FIGS. 2a-c, a conventional PZT micro-actuator 205 comprises a ceramic U-shaped frame 297. The frame 297 comprises two ceramic beams 207, each of which has a PZT element (not labeled) mounted thereon for actuation. The PZT micro-actuator 205 is operably coupled to a suspension 213, and there are multiple (e.g., three) electrical connection balls 209 (formed by, for example, gold ball bonding (GBB) or solder ball bonding (SBB)) to operably couple the micro-actuator 205 to the suspension traces 210 on one side of each of ceramic beam 207. In addition, there are multiple (e.g., four) metal balls 208 (formed by, for example, GBB or SBB) to operably couple the slider 203 to the suspension traces 210 for connection with read/write transducers (not shown). The micro-actuator 205 is mounted to the suspension tongue by the bottom arm of the frame 297, and the slider 203 is at least partially mounted between the two side arms 207 of the micro-actuator 205.
The slider 203 is connected (e.g. bonded using epoxy dots 212) to the two ceramic beams 207 at points 206 proximate to the opening of the U-shaped frame. The frame 297 is shaped like a hollow rectangular structure for receiving the slider 203. The bottom of the frame 297 is attached to the suspension tongue region of the suspension. The slider 203 and the beams 207 are not directly connected to the suspension and thus may move freely with respect to the suspension.
When an actuating power is applied through the suspension traces 210, the PZT pieces on the ceramic beams 207 will expand and/or contract, causing the two ceramic beams 207 to bend in a common lateral direction. The bending causes a shear deformation of the frame 297, whereby its shape resembles a parallelogram. The slider 203 undergoes a lateral translation, because it is attached to the moving side(s) of the parallelogram. Thus, a fine head position adjustment can be attained.
While these structures traditionally have been suitable for large (e.g., 3.5″) HDDs, several improvements still could be made. For example, 3.5″ HDDs typically have large platforms, and this arrangement generally helps to provide shock performance by maintaining sufficiently large margins. However, especially in the case of smaller HDDs (e.g., HDDs less than 3.5″ including, for example, 2.5″, 1.8″, and smaller platform HDDs), the large mass of the micro-actuator will negatively affect shock performance. Additionally, regardless of size, increased mass may negatively impact the resonance characteristics (relating to, for example, resonance frequencies, resonance gains, etc.), whereas reduced masses may provide improved resonance characteristics.
Thus it will be appreciated that there is a need in the art for an improved micro-actuator, HGA, and disk drive device, and methods of making the same.